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<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <script>
        //浮点型数据运算需要先转换为整型
      var num =0.1
      var num2=0.2
    //   console.log(num+num2)
      var c=(num*10+num2*10)/10
    //   console.log(c)
  console.log(typeof('hjahdjash'-1))//NaN Not a Number
// console.log(isNaN(num))

 //布尔值
 var a = false;
 var b = true;
 /* console.log(a+1)
 console.log(b+1) */

//String字符串类型 "" ''
var c='121'
var d = "121"
var e = '黄河是中国的"母亲河"'
console.log(e)
//转义符
console.log('黄河是中国的\n"母亲河"')
console.log(e.length)
console.log('黄河是中国的"母亲河"'+num)
console.log(undefined +11)
console.log(null +111)
    </script>
</body>
</html>